Tetrad formation in meiosis occurs in :-

Options

A. Leptotene
B. Zygotene
C. Pachytene
D. Diplotene

Answer

To answer the question "Tetrad formation in meiosis occurs in:", we need to analyze the stages of meiosis and identify where tetrads are formed.

### Step-by-Step Solution:

1. **Understanding Tetrad Formation**:
- A tetrad consists of a pair of homologous chromosomes, each made up of two sister chromatids. Therefore, a tetrad contains four chromatids in total.

2. **Identifying the Stages of Meiosis**:
- Meiosis consists of two main stages: Meiosis I and Meiosis II. Meiosis I is further divided into several phases: prophase I, metaphase I, anaphase I, and telophase I.

3. **Focusing on Prophase I**:
- Prophase I is the stage where tetrad formation occurs. It is divided into five substages: leptonema, zygonema, pachynema, diplonema, and diakinesis.

4. **Analyzing Each Substage**:
- **Leptonema**: Chromosomes begin to condense, but no tetrads are formed yet.
- **Zygonema**: Homologous chromosomes begin to pair up, but tetrads are not fully formed.
- **Pachynema**: This is the critical stage where tetrads are fully formed, and crossing over occurs between homologous chromosomes.
- **Diplonema**: The homologous chromosomes begin to separate slightly, but the tetrads are still visible.
- **Diakinesis**: The chromosomes condense further, and the tetrads are still present as they prepare for metaphase.

5. **Conclusion**:
- The correct answer to the question is that tetrad formation occurs during the **pachynema** stage of prophase I in meiosis.

### Final Answer:
Tetrad formation in meiosis occurs in **pachynema**.

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